Related Experiment Video
Updated: Apr 21, 2026
Isolation of mRNAs Associated with Yeast Mitochondria to Study Mechanisms of Localized Translation
Published on: March 14, 2014
Vesicular transport of a ribonucleoprotein to mitochondria
Joyita Mukherjee1, Biraj Mahato2, Samit Adhya3
1Genetic Engineering Laboratory, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Calcutta 700032, India Present address: Penn Institute for Regenerative Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104, USA.
Abstract:
Intracellular trafficking of viruses and proteins commonly occurs via the early endosome in a process involving Rab5. The RNA Import Complex (RIC)-RNA complex is taken up by mammalian cells and targeted to mitochondria. Through RNA interference, it was shown that mito-targeting of the ribonucleoprotein (RNP) was dependent on caveolin 1 (Cav1), dynamin 2, Filamin A and NSF. Although a minor fraction of the RNP was transported to endosomes in a Rab5-dependent manner, mito-targeting was independent of Rab5 or other endosomal proteins, suggesting that endosomal uptake and mito-targeting occur independently. Sequential immunoprecipitation of the cytosolic vesicles showed the sorting of the RNP away from Cav1 in a process that was independent of the endosomal effector EEA1 but sensitive to nocodazole. However, the RNP was in two types of vesicle with or without Cav1, with membrane-bound, asymmetrically orientated RIC and entrapped RNA, but no endosomal components, suggesting vesicular sorting rather than escape of free RNP from endosomes. In vitro, RNP was directly transferred from the Type 2 vesicles to mitochondria. Live-cell imaging captured spherical Cav1(-) RNP vesicles emerging from the fission of large Cav(+) particles. Thus, RNP appears to traffic by a different route than the classical Rab5-dependent pathway of viral transport.
Insights
The RNA Import Complex (RIC)-RNA complex targets mitochondria independently of endosomal pathways. This ribonucleoprotein (RNP) transport utilizes a novel route distinct from classical viral trafficking mechanisms.
Area of Science:
- Cell Biology
- Molecular Biology
- Virology
Background:
- Intracellular trafficking is crucial for viruses and proteins, often involving Rab5-mediated endosomal pathways.
- The RNA Import Complex (RIC)-RNA complex is taken up by mammalian cells and directed to mitochondria.
Purpose of the Study:
- To elucidate the intracellular trafficking pathway of the RIC-RNA complex to mitochondria.
- To determine if endosomal pathways, specifically Rab5-dependent routes, are involved in RIC-RNA mitochondrial targeting.
Main Methods:
- RNA interference to identify key proteins involved in mito-targeting.
- Sequential immunoprecipitation to analyze vesicle composition.
- In vitro assays to study vesicle-to-mitochondria transfer.
- Live-cell imaging to observe vesicle dynamics.
Main Results:
- Mito-targeting of the ribonucleoprotein (RNP) depends on caveolin 1 (Cav1), dynamin 2, Filamin A, and NSF, but is independent of Rab5 and endosomal proteins.
- RNP undergoes vesicular sorting, separating from Cav1 and endosomal components.
- RNP is found in distinct vesicles, facilitating direct transfer to mitochondria.
- Live-cell imaging reveals vesicle fission dynamics contributing to RNP transport.
Conclusions:
- The RIC-RNA complex utilizes a novel, non-endosomal pathway for mitochondrial targeting.
- This pathway involves specific protein dependencies and vesicular sorting distinct from canonical viral transport routes.
Related Concept Videos
01:19Translocation of Proteins into the Mitochondria
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
01:39Mitochondrial Protein Sorting
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
01:34Protein Transport into the Inner Mitochondrial Membrane
Transport of mitochondrial precursors across the TIM23 channel is driven by...
01:45Overview of Protein Sorting and Transport
Protein sorting can be of two types: signal-based sorting and vesicle-based trafficking. In signal-based sorting, specific amino acid sequences called sorting signals target proteins to the proper location inside the cell either via gated transport or by protein translocation. In gated transport, folded...
01:27Post-translational Translocation of Proteins to the RER
Targeting proteins to the ER
Hsp40 and Hsp70 chaperone molecules bind the translated proteins in the cytosol to prevent their folding. The chaperone binding helps to keep the signal...
02:22Regulated mRNA Transport